From 329485fe748d6c6f0740805efa2032cbd977a0db Mon Sep 17 00:00:00 2001
From: Jose Celano <josecelano@gmail.com>
Date: Wed, 20 Sep 2023 14:36:54 +0100
Subject: [PATCH] refactor: [#276] extract fn
 parse_torrent::decode_and_validate_torrent_file

---
 src/errors.rs              | 11 +++++++++++
 src/services/torrent.rs    | 18 ++++--------------
 src/utils/parse_torrent.rs | 38 ++++++++++++++++++++++++++++++++++++++
 3 files changed, 53 insertions(+), 14 deletions(-)

diff --git a/src/errors.rs b/src/errors.rs
index e8ef6712..b6f3385d 100644
--- a/src/errors.rs
+++ b/src/errors.rs
@@ -6,6 +6,7 @@ use hyper::StatusCode;
 
 use crate::databases::database;
 use crate::models::torrent::MetadataError;
+use crate::utils::parse_torrent::MetainfoFileDataError;
 
 pub type ServiceResult<V> = Result<V, ServiceError>;
 
@@ -215,6 +216,16 @@ impl From<MetadataError> for ServiceError {
     }
 }
 
+impl From<MetainfoFileDataError> for ServiceError {
+    fn from(e: MetainfoFileDataError) -> Self {
+        eprintln!("{e}");
+        match e {
+            MetainfoFileDataError::InvalidBencodeData => ServiceError::InvalidTorrentFile,
+            MetainfoFileDataError::InvalidTorrentPiecesLength => ServiceError::InvalidTorrentTitleLength,
+        }
+    }
+}
+
 #[must_use]
 pub fn http_status_code_for_service_error(error: &ServiceError) -> StatusCode {
     #[allow(clippy::match_same_arms)]
diff --git a/src/services/torrent.rs b/src/services/torrent.rs
index 7ae61848..dd13331f 100644
--- a/src/services/torrent.rs
+++ b/src/services/torrent.rs
@@ -17,7 +17,7 @@ use crate::models::torrent_file::{DbTorrent, Torrent, TorrentFile};
 use crate::models::torrent_tag::{TagId, TorrentTag};
 use crate::models::user::UserId;
 use crate::tracker::statistics_importer::StatisticsImporter;
-use crate::utils::parse_torrent;
+use crate::utils::parse_torrent::decode_and_validate_torrent_file;
 use crate::{tracker, AsCSV};
 
 pub struct Index {
@@ -134,20 +134,10 @@ impl Index {
 
         let metadata = self.validate_and_build_metadata(&add_torrent_req).await?;
 
-        // Validate and build torrent file
-
-        let original_info_hash = parse_torrent::calculate_info_hash(&add_torrent_req.torrent_buffer);
-
-        let mut torrent =
-            parse_torrent::decode_torrent(&add_torrent_req.torrent_buffer).map_err(|_| ServiceError::InvalidTorrentFile)?;
-
-        // Make sure that the pieces key has a length that is a multiple of 20
-        if let Some(pieces) = torrent.info.pieces.as_ref() {
-            if pieces.as_ref().len() % 20 != 0 {
-                return Err(ServiceError::InvalidTorrentPiecesLength);
-            }
-        }
+        let (mut torrent, original_info_hash) = decode_and_validate_torrent_file(&add_torrent_req.torrent_buffer)?;
 
+        // Customize the announce URLs with the linked tracker URL
+        // and remove others if the torrent is private.
         torrent.set_announce_urls(&self.configuration).await;
 
         let canonical_info_hash = torrent.canonical_info_hash();
diff --git a/src/utils/parse_torrent.rs b/src/utils/parse_torrent.rs
index 5644cd8d..e04c2549 100644
--- a/src/utils/parse_torrent.rs
+++ b/src/utils/parse_torrent.rs
@@ -1,5 +1,6 @@
 use std::error;
 
+use derive_more::{Display, Error};
 use serde::{self, Deserialize, Serialize};
 use serde_bencode::value::Value;
 use serde_bencode::{de, Error};
@@ -8,6 +9,43 @@ use sha1::{Digest, Sha1};
 use crate::models::info_hash::InfoHash;
 use crate::models::torrent_file::Torrent;
 
+#[derive(Debug, Display, PartialEq, Eq, Error)]
+pub enum MetainfoFileDataError {
+    #[display(fmt = "Torrent data could not be decoded from the bencoded format.")]
+    InvalidBencodeData,
+
+    #[display(fmt = "Torrent has an invalid pieces key length. It should be a multiple of 20.")]
+    InvalidTorrentPiecesLength,
+}
+
+/// It decodes and validate an array of bytes containing a torrent file.
+///
+/// It returns a tuple containing the decoded torrent and the original info hash.
+/// The original info-hash migth not match the new one in the `Torrent` because
+/// the info dictionary might have been modified. For example, ignoring some
+/// non-standard fields.
+///
+/// # Errors
+///
+/// This function will return an error if
+///
+/// - The torrent file is not a valid bencoded file.
+/// - The pieces key has a length that is not a multiple of 20.
+pub fn decode_and_validate_torrent_file(bytes: &[u8]) -> Result<(Torrent, InfoHash), MetainfoFileDataError> {
+    let original_info_hash = calculate_info_hash(bytes);
+
+    let torrent = decode_torrent(bytes).map_err(|_| MetainfoFileDataError::InvalidBencodeData)?;
+
+    // Make sure that the pieces key has a length that is a multiple of 20
+    if let Some(pieces) = torrent.info.pieces.as_ref() {
+        if pieces.as_ref().len() % 20 != 0 {
+            return Err(MetainfoFileDataError::InvalidTorrentPiecesLength);
+        }
+    }
+
+    Ok((torrent, original_info_hash))
+}
+
 /// Decode a Torrent from Bencoded Bytes.
 ///
 /// # Errors